1. Field of the Invention
This invention relates to a novel, curable urethane composition and to a process of preparing novel formulations using the same. More particularly, this invention relates to a novel, curable, one component, solventless, blocked isocyanate composition and to a process of preparing compositions using said novel, blocked isocyanate compositions.
2. Description of the Prior Art
Blocked isocyanate compositions are well known in the art. U.S. Pat. No. 3,583,943 teaches a curable coating composition comprising (a) a ketoxime, blocked isocyanate, terminated reaction product of a polyhydroxyl compound with an isocyanate, said reaction product having a molecular weight of from about 8,000 to about 15,000 and (b) a tertiary amino alcohol having at least two hydroxyl groups. U.S. Pat. No. 3,694,389 teaches a thermosetting coating composition comprising a ketoxime-blocked isocyanate and a solution copolymer of a mixture of ethylenically unsaturated and active hydrogen-containing compounds. U.S. Pat. No. 3,660,355 teaches novel thermosetting resin powders which can be molded to form urethane crosslinked products which are prepared by reacting hydroxyfunctional, acrylic polymer particles with a mono-blocked diisocyanate. U.S. Pat. No. 3,676,402 teaches octaalkyl-stannoxanes as regenerative agents of an isocyanate group and a blocked isocyanate compound at temperatures lower than previously possible. U.S. Pat. No. 3,857,818 teaches a powdered coating composition comprising a free flowing mixture of a solid, ketoximer-blocked isocyanate prepolymer and one or more solid, hydroxyfunctional resins such as the polyester resin. U.S. Pat. No. 3,984,365 teaches an aqueous solution of bisulfate-blocked polyisocyanate prepolymers having storage stability up to about 45.degree. C. by incorporation of about 0.5 to 20% by weight of the prepolymer of an aromatic or alkyl aromatic, sulfonic acid. U.S. Pat. No. 4,046,744 teaches a low temperature, one component, thermosetting coating composition comprising a ketoxime-blocked polyisocyanate and an oxazolidine. U.S. Pat. No. 4,403,086 teaches high solid, solvent-based, thermosetting resin coating compositions comprising chain-extendable, crosslinkable, low molecular weight polyol, diblocked diisocyanate and crosslinking agent reactive with a polyol, but substantially unreactive with the isocyanate functionality. U.S. Pat. No. 4,409,340 teaches a heat curable, coating composition comprising a prepolymer with ketoxime-blocked NCO groups which are linked to the prepolymer via cycloaliphatic and/or aliphatic groups, a diamine crosslinker and an organic solvent. U.S. Pat. No. 4,373,081 teaches thermally crosslinkable, coating compositions which are liquid and storage stable at room temperature and which contain combinations of dialkyl-malonate-blocked polyisocyanates and organic polyhydroxyl compounds as binders.
Additional patents in the literature which are involved with low temperature cured, blocked isocyanate compositions include U.S. Pat. No. 4,546,166; U.S. application having Ser. No. 333,810, filed Dec. 23, 1981; and German Offenlegungsschrift DE No. 32 28 670. However, most of the compositions cited do not provide sufficient shelf life. For instance, in U.S. Pat. No. 4,546,166, although it is claimed that the polyurethane composition can be cured at 80.degree.-100.degree. C., the cured time is much longer than the required 30 minutes (i.e., 2 to 4 hours), and the composition is not storage stable because polyisocyanates used are not blocked. In another case, i.e., U.S. application having Ser. No. 333,810, filed Dec. 23, 1981, although the composition is based on blocked isocyanate chemistry and the cured temperature reported is 115.degree. C. for 30 minutes, the composition is not solventless. Further, in the case where storage stability was claimed (for 2 months at room temperature) in German Offenlegungsschrift DE No. 32 28 670, the cured temperature is significantly higher, i.e., 140.degree. C., for 20 minutes.
In recent years, in the automotive industry, there has also been a drive towards lowering oven temperatures from about 140.degree. C.-120.degree. C. or lower. Polyvinyl chloride (PVC) plastisol is the major product being used in this area for sealant applications. PVC plastisols perform well at a processing temperature of 140.degree. C., but lose their adhesion strength when cured at 120.degree. C. due to poor plasticization. Thus, there has been a long-felt want for a material which is storage stable to be cured at 100.degree. C. with high adhesive strength.
A further typical problem generally connected with urethane chemistry is the high reactivity of the isocyanate groups with water releasing carbon dioxide gas that causes foaming problems in the material on curing.